The present invention relates to the general field of mounting an accessory driver unit on a turbojet.
In a turbojet, the accessories, such as the pumps for producing hydraulic energy, feeding fuel, and providing lubrication, and also the electricity generators for producing electrical power, etc. are grouped together within a unit commonly referred to as an accessory gearbox (AGB). Such a unit generally comprises one or more gear trains that are driven in rotation by power taken from a shaft of the turbojet and that are coupled to the various accessories.
In turbojets of the CFM® family, the AGBs are generally mounted in the zone or region of the fan compartment. More precisely, they are suspended from flanges formed on the metal blade-containment casing of said fan compartment.
However, the containment casings of fan compartments are being made more and more frequently out of a composite material in an attempt to save weight. Unfortunately, it is not easy to form flanges enabling an AGB to be attached on such casings made of composite material.
In addition, aircraft manufacturers require turbojets to supply ever higher levels of electrical power, which generally gives rise to two voluminous electricity generators being installed on the AGB. As a result, for an AGB mounted in the region of the fan compartment, the nacelle of the turbojet is enlarged in register with said AGB in order to limit the front area of the nacelle. Said enlargement nevertheless gives rise to aerodynamic impacts that are very penalizing in terms of performance.
In order to solve these problems, it is known to mount the AGB in the central compartment or “core” of the turbojet, and more particularly around the high-pressure compressor of the turbojet. However, that type of mounting leads to technical difficulties. In particular, installing a considerable load on the casing of the high-pressure compressor risks reducing the performance of said casing because of a phenomenon of ovalization of the casing (ovalization has a correspondingly greater effect when the diameter of the compressor casing is small). Furthermore, the presence of air tubes for discharging air upstream from the high-pressure compressor during some stages of flight limits the possibilities of attaching the AGB on components of the core compartment, other than on the casing of the high-pressure compressor.